Flexography Printing

ABSTRACT

A flexographic printing plate includes at least one halftone printing area with a plurality of halftone dots. A halftone dot of said plurality of halftone dots is shaped as a relief area. Said relief area includes a central portion and a surrounding portion. Said central portion has a central dot floor with a first pattern of a plurality of pins protruding upwardly from the central dot floor. Said surrounding portion protrudes upwardly from the central dot floor and has a top side including a second pattern of a plurality of recesses. The first pattern and second pattern are such that the surrounding portion can be distinguished from the central portion.

FIELD OF INVENTION

The field of the invention relates to flexography printing. Particularembodiments relate to a printing plate, in particular a flexographicprinting plate comprising at least one halftone printing area with aplurality of halftone dots, a method for producing a plate layout, amethod for making a flexographic printing plate, and a computer programproduct for performing steps of the method.

BACKGROUND

Flexography printing is a printing method that uses resilient reliefimage plates of a resilient material such as rubber, includingphotopolymers to print an image on diverse types of absorbent or nonabsorbent materials, such as plastic films, cardboard, etc., e.g. foruse in the packaging and label industry.

In prior art embodiments flexographic printing plates are arranged ontoa printing roller for printing. Ink is applied on the flexographicprinting plate using e.g. a metering roller. The material to be printedon, e.g supplied as a continuous web, is placed between the printingroller and a backing. The flexographic printing plate is brought againstthe material with a suitable pressure to allow contact between therelief image on the plate and the material.

Whenever relief areas contact the printed surface, one gets asubstantially solid colour area. To create a grey scale, a half-toningprocess is used. Using this process grey tones are reproduced byprinting a plurality of solid dots per unit area and varying either thefrequency of the dots per unit area and/or the size of the dots or both.

It was a problem in flexographic printing that solid areas, that isareas in the image where there are no halftone dots, as well as halftoneareas are difficult to print. To address this problem it is known to usesurface patterning. This technique consists in arranging a plurality ofsmall wells or pins in and/or on the top surface of the solid areas. Inthat way the ink on the solid areas is better distributed, increasingthe uniformity and saturation in the printed image. This surfacepatterning technique has also been used in halftone areas. However, whenthe size of a half-tone dot is relatively small, it has been found thatthe small wells and/or pins in/on the top surface of a halftone dote maydestabilize the halftone dot.

There is thus a need for flexographic printing plates that at leastpartially alleviate these problems and for a method preferablyimplemented at least partially through software, to produce such plates.

SUMMARY

Embodiments of the invention aim to provide a flexographic printingplate allowing improved printing of halftone areas and methodspreferably implemented at least partially through software and/orelectronics, to produce such plates.

According to a first aspect of the invention there is provided aflexographic printing plate comprising at least one halftone printingarea with a plurality of halftone dots. A halftone dot of said pluralityof halftone dots is shaped as a relief area comprising a central portionand a surrounding portion. The central portion has a central dot floorwith a first pattern of a plurality of pins protruding upwardly from thecentral dot floor. The surrounding portion protrudes upwardly from thecentral dot floor and has a top side comprising a second pattern of aplurality of recesses. The first pattern and second pattern are suchthat the surrounding portion can be distinguished from the centralportion.

Embodiments are based inter alia on the inventive insight that theupwardly protruding pins in the central portion will ensure that the inkis distributed and spread out in an improved manner across the centralportion whilst avoiding that too much ink is necessary. On the one hand,the surrounding portion will ensure that also for small halftone dotsthe relief is sufficiently stable whilst on the other hand the recessesin the surrounding portion will allow obtaining a good transitionbetween adjacent halftone dots, improving ink lay-down. By providing thesurrounding portion the stability of a halftone dot is improved, therebyallowing the pressure during printing and hence the productivity to beincreased. The second pattern of recesses in the surrounding portion incombination with the pins in the central portion will ensure thatsmoother halftone vignettes, in which the background fades graduallyaway until it blends into the unprinted paper or into white, areobtained.

In an exemplary embodiment the relief area is substantially circular.The diameter of the relief area is preferably between 10 and 1000micrometre, more preferably between 10 and 500 micrometre.

In an exemplary embodiment the surrounding portion is a substantiallyring shaped portion.

In an exemplary embodiment the plurality of recesses comprise any one ormore of the following: depressions, wells or pits, grooves. The groovesmay run from an inner edge of the surrounding portion to an outer edgeof the surrounding portion and may be applied parallel to each other.Preferably the plurality of recesses is distributed evenly across thesurrounding portion.

In an exemplary embodiment the first pattern is distinct from the secondpattern.

In an exemplary embodiment, seen in a top surface of the halftone dot,the pins form the first pattern, and the top side of the surroundingportion adjacent the recesses therein form a third pattern complementaryto the second pattern of the recesses, and the third pattern isdifferent from the first pattern. In other words, in certain embodimentsthe first and second pattern may be the same, e.g. the grid of pins inthe central portion may be the same as the grid of recesses in thesurrounding portion, but the third pattern formed by the area around therecesses, i.e. the area which has a top surface at the same level as thepins, is different from the first pattern.

In an exemplary embodiment the plurality of recesses have a depth whichis larger than 1 micrometre, preferably larger than 2 micrometre, morepreferably larger than 5 micrometre, most preferably larger than 10micrometre, and e.g. between 20 and 70 micrometre.

In an exemplary embodiment, seen in a top surface of the surroundingportion, the surface area of the plurality of recesses is at least 1% ofthe surface area of the surrounding portion, preferably at least 5% ofthe surface area of the surrounding portion, more preferably at least20%. In an exemplary embodiment the surface area of the plurality ofrecesses is between 5 and 50% of the surface area of the surroundingportion

In an exemplary embodiment the plurality of pins have a height which islarger than 1 micrometre, preferably larger than 2 micrometre, morepreferably larger than 5 micrometre, most preferably larger than 10micrometre, and e.g. between 20 and 70 micrometre.

In an exemplary embodiment the plurality of pins have dimensions, seenin the plane of the central dot floor, between 1 and 100 micrometre,preferably between 5 and 50 micrometre, and e.g. between 5 and 20micrometre.

In an exemplary embodiment the plurality of pins are distributed evenlyacross the central portion. The pins typically have a pillar shape witha substantially square, rectangular or round cross section, or a shapebetween square and round. The pillar shape may be conical or pyramidal,or substantially cylindrical. When diffuse light is used, the shape maybe more conical or pyramidal, but when LED or laser light is used thewalls of the pins may be more vertical. The skilled person understandsthat the shape will be dependent on the process used for creating thepins.

In an exemplary embodiment, seen in a plane of the central dot floor,the surface area of the plurality of pins is smaller than the surfacearea of the central dot floor.

In an exemplary embodiment, seen in the plane of the central dot floor,the surface area of the plurality of pins is larger than 5% of thesurface area of the central portion, preferably between 5% and 75% ofthe surface area of the central portion, more preferably between 10% and50%, and most preferably between 15 and 40%.

According to another aspect there is provided a method for generating aplate layout for making a flexographic printing plate. The plate layoutrepresents an image having solid image areas, halftone image areas, andareas that need not be printed. The method comprises the steps of:receiving digital values representing point by point an image to beprinted; and generating a plate layout in which the digital values havebeen converted into binary data allowing to form the halftone imageareas and the solid image areas, wherein for the halftone image areas atleast a tile associated with a halftone dot is calculated. The tilecontains a plurality of pixels arrayed in two dimensions. The tile iscalculated such that it contains a central portion with a first patternof a plurality of pins, and a surrounding portion comprising a secondpattern of a plurality of recesses. The plurality of pins is representedby a binary value different from the rest of the central portion. Theplurality of recesses is represented by a binary value different fromthe plurality of pins and different from the rest of the surroundingportion. The first pattern and second pattern are such that thesurrounding portion can be distinguished from the central portion.

According to another aspect there is provided a method for making aflexographic printing plate. The method comprises a method forgenerating a plate layout as set out above, and using the generatedplate layout to make the flexographic printing plate. This may involve:producing a screened film intermediate using the generated plate layout,and using said screened film intermediate to write the flexographicprinting plate; or removing portions of a laminated layer, e.g. a carbonlayer of the flexographic printing plate using the generated platelayout, and writing the flexographic printing plate through the removedportions of the laminated layer; or using the generated plate layout toproduce directly the flexographic printing plate.

In an exemplary embodiment the central portion in the tile issubstantially circular, and the surrounding portion in the tile issubstantially ring shaped.

In an exemplary embodiment the plurality of pixels of the tilerepresents an area with a length and width dimension between 10 and 1000micrometre, more preferably between 10 and 500 micrometre.

In an exemplary embodiment each recess of the plurality of recesses isrepresented by a group of adjacent pixels, said group of adjacent pixelspreferably having a step-shape. Such a step shape will allow creatingrecesses in the form of grooves.

In an exemplary embodiment the number of pixels representing theplurality of recesses is at least 1% of the total number of pixelsrepresenting the surrounding portion, preferably at least 5%, morepreferably at least 20% and e.g. between 5% and 50%.

In an exemplary embodiment pixels representing the plurality of recessesare distributed evenly across the surrounding portion. In an exemplaryembodiment pixels representing the plurality of pins are distributedevenly across the central portion.

In an exemplary embodiment the number of pixels representing of theplurality of pins is more than 5% of the total number of pixelsrepresenting the central portion, preferably between 5% and 75% of thetotal number of pixels representing the central portion, more preferablybetween 10% and 50%, and most preferably between 15% and 40%.

According to an exemplary embodiment the flexographic printing plate ismade of rubber or of a variety of radiation sensitive polymer resins,typically sensitive to ultraviolet radiation. The flexographicphotosensitive polymer resin plate may be a solvent based plateconfigured to be developed using a solvent, a water based plateconfigured to be developed using water, a thermal based plate configuredto be developed by heating, a direct write plate, etc.

According to a further aspect of the invention, there is provided acomputer program comprising computer-executable instructions to performthe method, when the program is run on a computer, according to any oneof the steps of any one of the embodiments disclosed above.

According to a further aspect of the invention, there is provided acomputer device or other hardware device programmed to perform one ormore steps of any one of the embodiments of the method disclosed above.According to another aspect there is provided a data storage deviceencoding a program in machine-readable and machine-executable form toperform one or more steps of any one of the embodiments of the methoddisclosed above.

BRIEF DESCRIPTION OF THE FIGURES

The accompanying drawings are used to illustrate presently preferrednon-limiting exemplary embodiments of devices of the present invention.The above and other advantages of the features and objects of theinvention will become more apparent and the invention will be betterunderstood from the following detailed description when read inconjunction with the accompanying drawings, in which:

FIG. 1 illustrates schematically a cross section of a halftone dot in anexemplary embodiment;

FIG. 2 illustrates schematically a top view of the halftone dot of FIG.1;

FIG. 3 illustrates schematically a top view of a halftone dot accordingto an exemplary embodiment;

FIG. 4 illustrates schematically a tile for use in exemplary embodimentsof the invention;

FIGS. 5A-5C illustrate top views of a halftone area of a plate accordingto an exemplary embodiment for different dot coverage percentages;

FIGS. 6A-6C illustrate perspective views of a halftone area of a plateaccording to an exemplary embodiment for different dot coveragepercentages;

FIGS. 7A and 7B illustrate gradient circles and strips using anembodiment without a second pattern and with a second pattern on thesurrounding portion of the halftone dots, respectively; and

FIG. 8 illustrates a flow chart of an exemplary embodiment of the methodof the invention.

DESCRIPTION OF EMBODIMENTS

Throughout the following detailed description, similar referencenumerals refer to similar elements in all figures of the drawings.

Images typically reproduced by flexographic plates typically includeboth solid image areas and a variety of grey tone areas, also calledhalftone areas. By solid areas we mean image areas completely covered byink having the highest density the ink can produce on a print material.By grey tone or halftone areas we mean image areas where the appearanceof the printed image is of a density intermediate to pure white (totalabsence of ink) and solid. Grey areas are produced by the process ofhalf-toning, wherein a plurality of relief surface areas per unit areais used to produce the illusion of different density printing. Theserelief areas are commonly referred to in the printing industry as“halftone dots”. Image presentation is achieved by changing a percentageof area coverage (dot intensity) from region to region. Dot intensitymay be altered by altering the dot size and/or the dot density, i.e. thedot frequency.

In a flexographic plate, the halftone dots are relief areas having theirsurface at the top surface of the plate. The plate in the areasurrounding the dot has been etched to a depth which reaches to a floor.The height of a halftone dot is the distance of the surface of the dot(and of the plate surface) to the floor. The halftone relief is therelief extending from the floor to the top surface. This relief maydecrease as the dot coverage percentage increases, but will besufficient to confine ink to the dot surface.

The invention relates to an improved technique for printing withflexographic printing plates, and in particular a technique which allowsobtaining good results when printing halftone areas with halftone dots.Such a halftone dot is shaped preferably as a substantially circularrelief area of the printing plate.

FIGS. 1 and 2 illustrate a cross section and a top view of a halftonedot with a substantially circular relief area 30 of a flexographicprinting plate. The halftone dot can have a diameter between 10 and 1000micrometre, e.g. about 50 μm. The relief area 30 comprises a centralportion 10 surrounded by a surrounding portion, here a ring portion 20.The central portion 10 has a central dot floor 25 with a first patternof a plurality of pins 11 protruding upwardly from the central dot floor25. The ring-shaped portion 20 protrudes upwardly from the central dotfloor 25 and is provided with a plurality of recesses 21. The recesses21 may be small depressions, wells or pits, but may also be grooves, seeFIG. 3. More generally any pattern of recesses may be used.

The upwardly protruding pins 11 in the central portion 10 will ensurethat the ink is distributed/spread out in an improved manner across thecentral portion 10 whilst avoiding that too much ink is necessary. Therecesses 21 in the protection ring 20 will weaken ring 20 and will allowobtaining a good transition between adjacent halftone dots and improvingink lay-down.

These recesses 21 do not extend to the floor 50 but are rather shallowin depth and are arrayed in a much higher frequency pattern than thehalftone dots 100. The recesses 21 may have a depth e.g. between 1 and70 micrometre. For example the halftone dot pattern in flexographicplates is of the order of a 75-200 lines per inch while the recesses arearrayed at frequencies which are e.g. at least ten times higher. Theshallow recesses 21 and the shallow areas between pins 11 behave asanchor regions for the ink film I creating a substantially even inkdistribution.

Seen in a top surface of the surrounding portion 20, the surface area ofthe recesses 21 is preferably at least 30% of the surface area of thesurrounding portion, preferably at least 40% of the surface area of thesurrounding portion. Preferably, the recesses 21 are distributed evenlyacross the surrounding portion 20.

The pins 11 may have a height e.g. between 10 and 70 micrometre. Thepins 11 may be distributed evenly across the central portion 10, butalso other patterns are possible, e.g. less dense towards the centre ofthe central portion 10. The pins 11 may have dimensions, seen in asection parallel to the central dot floor 25, between 1 and 100micrometre. Seen in a top surface of the central portion 10, the surfacearea of the pins 11 may be between e.g. 10% and 50% of the surface areaof the central portion, preferably between 15% and 40%.

In the embodiments of FIGS. 1-3 the first pattern of the pins 11 isdistinct from the second pattern of the recesses 21. However, in theembodiment of FIGS. 1 and 2, the first pattern could be identical to thesecond pattern in the sense that the dimensions of the pins 11 andrecesses 21 could be the same and that the pins 11 could be arranged ina grid with the same spacing between adjacent pins 11 as betweenadjacent recesses 21. However, seen in a top surface of the halftonedot, the area(s) of the surrounding portion arranged around/adjacent therecesses 21 form(s) a third pattern complementary to the second patternof the recesses 21, and the third pattern is different from the firstpattern. In fact the third pattern is the inverse of the first pattern,making the surrounding portion 20 distinguishable from the centralportion 10.

To produce an embodiment of a flexographic printing plate according tothe present invention, typically first a plate layout of the image to beprinted is generated. A plate layout is a binary representation of thecontinuous tone image in which grey scale tones have been reproduced ashalftones. When multiple colour printing is involved there will be aplurality of such plate layouts each representing a colour separation asis well known in the art. These plate layouts may then be used by acomputer controlled film exposure device such as an image setter, e.g. alaser printer, and an associated suitably programmed computer withsoftware to write the flexographic printing plate, either directly ofvia a film intermediate or laminate layer, see further. The software mayreceive digital values representing point by point a continuous toneoriginal image. In an 8 bit system, these values range from 0-255, withwhite being at one end of the scale and black at the other. Depending onwhether the system is a negative or a positive working system, 0 or 255represent a fully inked or solid area. We will assume in this discussionthat solids are represented by the digital value 255. The software nextscreens the image, that is generates a plate layout in which the 8 bitdigital values have been converted to binary (on-off) data that is fedto an image setter to control the exposing beam on or off in a way toform the solid areas and the halftone areas with halftone dots. To forma solid area, the exposing source may be ON all the time it is scanningthe solid area. A halftone dot is created within a tile consisting of aplurality of pixels usually representing the minimum spot size of theexposing source. A plurality of adjacent tiles forms an image area ofthe plate layout. The source is then used to obtain a dot shape byexposing preselected pixels within each tile. The exposing source may bee.g. a laser having e.g. a laser beam focussed to a pixel size of a fewmicrons, e.g. 1 to 20 microns. In other words, to make a halftone dot, atile is first calculated. The tile consists of a predetermined number ofpixels arrayed in two dimensions along the scanning path of the source.These tiles are repeated side by side to cover an area, or may bedistributed more or less randomly across an area. Depending on thedesired grey scale, the tile may contain adapted patterns for thecentral portion and/or for the surrounding portion, and/or the distancebetween adjacent tiles may be varied. The most common halftone dot shapeis one that approximates a circle, but the skilled person understandsthat other shapes, e.g. an ellipse shape, are possible.

FIG. 4 shows an exemplary tile 40 of a plate layout used to generate ahalftone dot using an image setter controlled by software. This exampleshows a tile 40 in the form of an 38*38 pixel array. Each of the pixels41 in the tile 40 is associated by a digital address. To generate ahalftone dot, the exposure source, e.g. a scanning laser exposes anumber of pixels 43 within a tile 40 whilst not exposing other pixels 42in the tile. This number may be related to the % halftone dot called forin that area of the plate. The exposed pattern of pixels is such that asubstantially circular dot 100 is formed having a central portion 10with a number of pins 11 and a ring shaped portion 20 with a pluralityof recesses 21.

FIG. 8 illustrates an embodiment of the method of the invention formaking a flexographic printing plate. In a first step 801 digital valuesrepresenting point by point an image to be printed are received. In asecond step 802 a plate layout in which the digital values have beenconverted into binary data allowing forming the halftone image areas andthe solid image areas, is generated. In step 802, for generating thehalftone image areas of the plate layout, at least a tile associatedwith a halftone dot is calculated, said tile containing a plurality ofpixels arrayed in two dimensions. The tile is calculated such that itcontains a central portion with a first pattern of a plurality of pins,the plurality of pins being represented by a binary value different fromthe rest of the central portion; and a surrounding portion comprising asecond pattern of a plurality of recesses, the plurality of recessesbeing represented by a binary value different from the rest of thesurrounding portion. The the first pattern and second pattern are suchthat the surrounding portion can be distinguished from the centralportion.

In an embodiment, the generated plate layout is used to produce ascreened film intermediate, see step 803 a. This film intermediate isplaced on a photopolymerizable plate and the plate is exposed throughthe screened film intermediate to radiation, e.g. UV radiation, see step804 a. The polymer material under the exposed pixels 43 remainsunpolymerized. Following UV radiation the unpolymerized areas in theplate are washed off.

In another embodiment the generated plate layout is used for removing,e.g. by laser burning, portions of a laminated layer, e.g. a carbonlayer, of the flexographic printing plate, see step 803 b. Theflexographic printing plate may then be written through the removedportions of the laminated layer, see step 804 b.

In yet other embodiments, the use of a physical screened intermediate(as in steps 803 a and 803 b) may be omitted and the photopolymerizableplate may be produced directly using the generated plate layout, seestep 804 c. Two variants thereof exist. According to a first variant ina first step the flexographic plate comprises a soft rubber layer whichis written, e.g. using UV light, and in a following step the non writtenareas are removed. According to a second variant the flexographic platecomprises a hard rubber layer which is ablated, using e.g. a powerfulCO2 or infrared laser, such that material is removed where needed and nofurther step is necessary. The software may then control directly eithera radiation source, e.g. a UV light source or a powerful laser toproduce without intermediate a printing plate comprising halftone areasof embodiments of the invention.

Halftone relief may be controlled by a number of other factors,including the process used to remove the material from the between thedots. In a photopolymer flexographic printing plate the maximum reliefmay be controlled by the back exposure of the plate which hardens thephotopolymer to a given depth and establishes a maximum relief.

The resulting plate can be mounted on a printing roller. In order toproduce good quality images the ink is preferably applied to theprinting material in a uniform and predictably manner. This in turnrequires that the relief areas in the flexographic plate carry ink in auniform layer and in predictable amounts. The amount of ink applied tothe printing plate may be controlled using a metering roller, e.g. ananilox roller. Anilox rollers have on their surface a cell patterncomprising a plurality of ink metering cells.

In embodiments of the invention the plate ink carrying capacity per unitarea is preferably less than the ink carrying capacity of the aniloxroller that is being used to transfer ink to the flexographic plate.Preferably the size of the recesses and the pins are adapted in functionof the size of the cells of the anilox roller.

FIGS. 5A, 5B, and 5C show top views of a halftone area of a plate forthree dot coverage percentages, namely 50%, 80%, and 85%, and FIGS. 6A,6B, and 6C show perspective views of a halftone area of a plate forthree dot coverage percentages, namely 50%, 80%, and 85%. The increasedpercentage is realised by increasing the halftone dot size: in FIG. 5Athe percentage is 50% and the number of pins 11 (shown in white) in thecentral portion 10 is approximately eight; in FIG. 5B the percentage is85% and the number of pins 11 (indicated in white) in the centralportion 10 is approximately twenty; etc. The surrounding portions 20 areprovided with grooves 21. The areas between the grooves 21 are shown inwhite in FIGS. 5A-5C and 6A-6C, and the grooves 21 are shown in black.As the percentage area coverage increases, the halftone dots 100eventually contact and merge with each other. After a predeterminedcoverage percentage is reached one no longer has isolated relief areasper halftone dot 100, but instead isolated holes separating the halftonedots 100 can be seen, see FIGS. 5B, and 5C. The holes extend from thesurface of the plate toward the floor. The ring shaped portions 20 ofthe halftone dots merge with each other, see FIGS. 5B and 5C.

FIGS. 7A and 7B illustrate gradient circles and strips using anembodiment without a second pattern and with a second pattern on thesurrounding portion of the halftone dots, respectively. It can be seenthat for the embodiment with a solid surrounding portion (FIG. 7A), i.e.a surrounding portion without a second pattern of recesses, the gradientcircles show abrupt changes at C1 and C2. Using an embodiment of theinvention with a surrounding portion in which a second pattern ofrecesses is arranged (FIG. 7B), the gradient circles vary more smoothly.By providing the surrounding portion the stability of a halftone dot isimproved, thereby allowing the pressure during printing and hence theproductivity to be increased. The second pattern of recesses in thesurrounding portion in combination with the pins in the central portionensures that smooth halftone gradients are obtained, in which thebackground fades gradually away until it blends into the unprintedpaper.

A person of skill in the art would readily recognize that steps ofvarious above-described methods can be performed by programmedcomputers. Herein, some embodiments are also intended to cover programstorage devices, e.g., digital data storage media, which are machine orcomputer readable and encode machine-executable or computer-executableprograms of instructions, wherein said instructions perform some or allof the steps of said above-described methods. The program storagedevices may be, e.g., digital memories, magnetic storage media, harddrives, or optically readable digital data storage media. Theembodiments are also intended to cover computers programmed to performsaid steps of the above-described methods.

Whilst the principles of the invention have been set out above inconnection with specific embodiments, it is to be understood that thisdescription is merely made by way of example and not as a limitation ofthe scope of protection which is determined by the appended claims.

1. A flexographic printing plate comprising at least one halftoneprinting area with a plurality of halftone dots; wherein a halftone dotof said plurality of halftone dots is shaped as a relief area; saidrelief area comprising a central portion and a surrounding portion; saidcentral portion having a central dot floor with a first pattern of aplurality of pins protruding upwardly from the central dot floor; saidsurrounding portion protruding upwardly from the central dot floor andhaving a top side comprising a second pattern of a plurality ofrecesses; wherein the first pattern and second pattern are such that thesurrounding portion can be distinguished from the central portion. 2.The flexographic printing plate of claim 1, wherein the relief area issubstantially circular.
 3. The flexographic printing plate of claim 1,wherein the diameter of the relief area is between 10 and 1000micrometres.
 4. The flexographic printing plate of claim 1, wherein thesurrounding portion is a substantially ring shaped portion.
 5. Theflexographic printing plate of claim 1, wherein the plurality ofrecesses comprise any one or more of the following: depressions, wellsor pits, grooves.
 6. The flexographic printing plate of claim 1, whereinthe first pattern is distinct from the second pattern; and/or wherein,seen in a top surface of the halftone dot, the top side of thesurrounding portion adjacent the recesses therein form a third patterncomplementary to the second pattern of the recesses, and the thirdpattern is different from the first pattern.
 7. The flexographicprinting plate of claim 1, wherein, seen in a top surface of thesurrounding portion, the surface area of the plurality of recesses is atleast 1% of the surface area of the surrounding portion.
 8. Theflexographic printing plate of claim 1, wherein the plurality ofrecesses are distributed evenly across the surrounding portion.
 9. Theflexographic printing plate of claim 1, wherein the plurality of pinshave a height which is higher than 1 micrometre; and/or wherein theplurality of recesses have a depth which is higher than 1 micrometre.10. The flexographic printing plate of claim 1, wherein the plurality ofpins are distributed evenly across the central portion.
 11. Theflexographic printing plate of claim 1, wherein the plurality of pinshave dimensions, seen in the plane of the central dot floor, between 1and 100 micrometre.
 12. The flexographic printing plate of claim 1,wherein, seen in the plane of the central dot floor, the surface area ofthe plurality of pins is larger than 5% of the surface area of thecentral portion.
 13. A method for generating a plate layout for making aflexographic printing plate, said plate layout representing an imagecomprising solid image areas and halftone image areas, said methodcomprising: receiving digital values representing point by point animage to be printed; generating a plate layout in which the digitalvalues have been converted into binary data allowing to form thehalftone image areas and the solid image areas, wherein for the halftoneimage areas at least a tile associated with a halftone dot iscalculated, said tile containing a plurality of pixels arrayed in twodimensions; wherein the tile is calculated such that it contains acentral portion with a first pattern of a plurality of pins; theplurality of pins being represented by a binary value different from therest of the central portion; and a surrounding portion comprising asecond pattern of a plurality of recesses; the plurality of recessesbeing represented by a binary value different from the rest of thesurrounding portion; wherein the first pattern and second pattern aresuch that the surrounding portion can be distinguished from the centralportion.
 14. The method of claim 13, wherein the central portion and thesurrounding portion are substantially circular.
 15. The method of claim13, wherein the plurality of pixels of the tile represents an area witha length and width dimension between 10 and 1000 micrometres.
 16. Themethod of claim 13, wherein each recess of the plurality of recesses isrepresented by a group of adjacent pixels, said group of adjacent pixelshaving a step-shape.
 17. The method of claim 13, wherein, the number ofpixels representing the plurality of recesses is at least 1% of thetotal number of pixels representing the surrounding portion.
 18. Themethod of claim 13, wherein pixels representing the plurality ofrecesses are distributed evenly across the surrounding portion; and/orwherein pixels representing the plurality of pins are distributed evenlyacross the central portion; and/or wherein the number of pixelsrepresenting of the plurality of pins is larger than 5% of the totalnumber of pixels representing the central portion. 19.-20. (canceled)21. A method for making a flexographic printing plate, said methodcomprising the method of claim 13, and using the generated plate layoutto make the flexographic printing plate through any one of the followingtechniques: producing a screened film intermediate using the generatedplate layout, and using said screened film intermediate to write theflexographic printing plate; or removing portions of a laminated layerof the flexographic printing plate using the generated plate layout, andwriting the flexographic printing plate through the removed portions ofthe laminated layer; or using the generated plate layout to producedirectly the flexographic printing plate.
 22. A computer program productencoding a program in machine-readable and machine-executable form toperform one or more steps of the method of: receiving digital valuesrepresenting point by point an image to be printed; generating a platelayout in which the digital values have been converted into binary dataallowing to form the halftone image areas and the solid image areas,wherein for the halftone image areas at least a tile associated with ahalftone dot is calculated, said tile containing a plurality of pixelsarranged in two dimensions; wherein the the is calculated such that itcontains a central portion with a first pattern of a plurality of pins;the plurality of pins being represented by a binary value different fromthe rest of the central portion; and a surrounding portion comprising asecond pattern of a plurality of recesses; the plurality of recessesbeing represented by a binary value different from the rest of thesurrounding portion; wherein the first pattern and second pattern aresuch that the surrounding portion can be distinguished from the centralportion.